1. Field of the Invention
The invention relates to a control apparatus of an engine, and more particularly, to a control apparatus of an engine capable of executing both an intake passage fuel injection and an in-cylinder fuel injection.
2. Description of the Related Art
So-called dual fuel injector engines are known which are provided with an intake passage fuel injector for injecting fuel into an intake passage, and an in-cylinder fuel injector for injecting fuel into a cylinder. It is also well known that in this kind of dual fuel injector engine the total injection quantity during one injection cycle is divided between the two injectors and the distribution ratio of that fuel injection quantity is changed according to the operating state of the engine. Technology related to this is described in Japanese Patent Application Publication No. JP-A-2001-20837, for example.
When executing air-fuel ratio control to bring the air-fuel ratio close to a predetermined target air-fuel ratio, it is desirable to make appropriate corrections that take into account combustion characteristics and the like determined by the operating state of the engine. Otherwise, even if a fuel injection quantity is corrected, the air-fuel ratio may conversely become even farther away from the target air-fuel ratio. Also, it is preferable that the air-fuel ratios in all of the cylinders match the target air-fuel ratio, though in actuality there is some degree of variation between cylinders. This variation is caused by individual differences due to, for example, injector manufacturing errors. Moreover, when the injection is divided up, the number of injectors that inject fuel increases while the injection quantity per injector decreases. As a result, the air-fuel ratio deviates even farther from the target air-fuel ratio, which is undesirable for performing accurate air-fuel ratio control.